<template>
  <scroll class="listview"
          :data="data1"
          :listen-scroll="lisScroll"
          @scroll="scrollListen"
          :probe-type="probeType"
          ref="listview">
    <template v-slot:scroll>
      <ul>
        <li v-for="(group, index) in data1" :key="index" class="list-group" ref="listGroup">
          <h2 class="list-group-title">{{group.title}}</h2>
          <ul>
            <li v-for="(item, index1) in group.items" :key="index1" @click="selectItem(item)" class="list-group-item">
              <img class="avatar" v-lazy="item.avater" alt="">
              <span class="name">{{item.name}}</span>
            </li>
          </ul>
        </li>
      </ul>
      <div class="list-shortcut" @touchstart="onShortcutStart" @touchmove.stop.prevent="onShortcutTouchMove">
        <ul>
          <li v-for="(item, index) in shortSutList" :key="index" class="item"
              :data-index="index" :class="{'current':currentIndex === index}">
            {{item}}
          </li>
        </ul>
      </div>
      <div class="list-fixed" v-show="fixedTitle" ref="fixed">
        <h1 class="fixed-title">{{fixedTitle}}</h1>
      </div>
    </template>
  </scroll>
</template>

<script>
import Scroll from '../scroll/scroll'
import { getData } from '@/common/js/dom'

const ANCHOR_HEIGHT = 18
const TITLE_HEIGHT = 30
export default {
  name: 'listview',
  components: { Scroll },
  props: {
    data1: {
      type: Array,
      default: null
    }
  },
  data () {
    return {
      lisScroll: true,
      scrollY: -1,
      currentIndex: 0,
      listHeight: [],
      probeType: 3,
      diff: -1
    }
  },
  created () {
    this.touch = {}
  },
  computed: {
    shortSutList() {
      return this.data1.map((group) => {
        return group.title.substr(0, 1)
      })
    },
    fixedTitle() {
      if (this.scrollY > 0) {
        return ''
      }
      return this.data1[this.currentIndex] ? this.data1[this.currentIndex].title : ''
    }
  },
  mounted () {
    // setTimeout(() => {
    //   this._calculateHeight()
    // }, 20)
  },
  methods: {
    selectItem(item) {
      this.$emit('select', item)
    },
    onShortcutStart(e) {
      let anchorIndex = getData(e.target, 'index')
      let firstTouch = e.touches[0]
      this.touch.y1 = firstTouch.pageY
      this.touch.anchorIndex = anchorIndex
      this._scrollTo(anchorIndex)
    },
    onShortcutTouchMove(e) {
      let firstTouch = e.touches[0]
      this.touch.y2 = firstTouch.pageY
      let dalta = (this.touch.y2 - this.touch.y1) / ANCHOR_HEIGHT | 0
      let anchorIndex = parseInt(this.touch.anchorIndex) + dalta
      this._scrollTo(anchorIndex)
    },
    scrollListen (pos) {
      // console.log('ok')
      this.scrollY = pos.y
    },
    _scrollTo(index) {
      // this.scrollY = -this.listHeight[index]
      this.$refs.listview.scrollToElement(this.$refs.listGroup[index], 0)
    },
    _calculateHeight () {
      this.listHeight = []
      const list = this.$refs.listGroup
      let height = 0
      this.listHeight.push(height)
      for (let i = 0; i < list.length; i++) {
        let item = list[i]
        height += item.clientHeight
        this.listHeight.push(height)
      }
    }
  },
  watch: {
    data1() {
      setTimeout(() => {
        // console.log('_calculateHeight')
        this._calculateHeight()
      }, 20)
    },
    scrollY(newY) {
      const listHeight = this.listHeight
      if (newY > 0) {
        this.currentIndex = 0
        return
      }
      for (let i = 0; i < listHeight.length - 1; i++) {
        let height1 = listHeight[i]
        let height2 = listHeight[i + 1]
        if ((-newY >= height1 && -newY < height2)) {
          this.currentIndex = i
          this.diff = height2 + newY
          return
        }
      }
      this.currentIndex = listHeight.length - 2
    },
    diff (newVal) {
      let fixTop = (newVal > 0 && newVal < TITLE_HEIGHT) ? newVal - TITLE_HEIGHT : 0
      if (this.fixedTop === fixTop) {
        return
      }
      this.fixedTop = fixTop
      this.$refs.fixed.style.transform = `translate3d(0,${fixTop}px,0)`
    }
  }
}
</script>

<style lang="stylus" scoped>
  @import "~@/common/stylus/variable"
  .listview
    position: relative
    width: 100%
    height: 100%
    overflow: hidden
    background: $color-background
    .list-group
      padding-bottom: 30px
      .list-group-title
        height: 30px
        line-height: 30px
        padding-left: 20px
        font-size: $font-size-small
        color: $color-text-l
        background: $color-highlight-background
      .list-group-item
        display: flex
        align-items: center
        padding: 20px 0 0 30px
        .avatar
          width: 50px
          height: 50px
          border-radius: 50%
        .name
          margin-left: 20px
          color: $color-text-l
          font-size: $font-size-medium
    .list-shortcut
      position: absolute
      z-index: 30
      right: 0
      top: 50%
      transform: translateY(-50%)
      width: 20px
      padding: 20px 0
      border-radius: 10px
      text-align: center
      background: $color-background-d
      font-family: Helvetica
      .item
        padding: 3px
        line-height: 1
        color: $color-text-l
        font-size: $font-size-small
        &.current
          color: $color-theme
    .list-fixed
      position: absolute
      top: 0
      left: 0
      width: 100%
      .fixed-title
        height: 30px
        line-height: 30px
        padding-left: 20px
        font-size: $font-size-small
        color: $color-text-l
        background: $color-highlight-background
    .loading-container
      position: absolute
      width: 100%
      top: 50%
      transform: translateY(-50%)

</style>
